Means for the projection of cinematograph films



G. B. BOWELL MEANS FOR THE PROJECTION OF CINEMATOGRAPH FILMS Filed Aug. 27. 1921 2 Sheets-Sheet 1 M7, Z a

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E5. BCIMELL MEANS FOR THE PROJECTION OF CINEMA; )L'J'HAPI-I FILMS FiledAug. 27, 1921 .2 snema smen 2 Patented Dec. 4, 1923.

UNITED STATES PATENT OFFICE.

B. BOWELL, OF HIGH BARNET, ENGLAND, ASSIGNOR OF ONE-HALF TO GILBERT RICHARD REDGRAVE, OF LONDON, ENGLAND.

MEANS FOR THE PRGJECTION OF CINEMATOGRAPE FILMS.

Application filed August 27, 1921. Serial No. 496,061.

To all whom it may concern:

Be it known that I, Gnoncn BnNNn'rr Bownnn, a subject of the King of Great Britain and Ireland, residing at :ZQBedford Avenue, High Barnet, Hertfordshire, England, have invented new and useful Improved Means for the Projection of Cinema tograph Films (on which application has been made for Letters Patent in Great Britain, No. 25,986, filed 8th September, 1920), of which the following is a specification.

The present invention relates to improved means for the projection. of cinematograph films. in the ordinary construction. of pr0- jecting mechanisms the film is intermittently advanced picture by picture usuallyat the rate of sixteen per second, the light necessarily'being obturated during the change to the next picture and since obturations at so slow a rate as sixteen ,per second must of necessity cause severe flickering, it is usual to form the shutter so as to give two extra obturations during the cycle of each film change. It has further been well established that all these obturations ought to be of equal duration, and that each duration should take one sixth of the time occupied by each cycle. This however, involves difficulties as it necessitates starting moving and stopping the film in a time approxi mately equal to one eighth of a sixteenth of a second.

in order to preventthe flickering which occurs from intermittently moving films, it was proposed ,many years ago to employ a continuously moving film and to deflect the beam of light through an arrangement of moving mirrors.

Briefly stated the present invention comprises the use in such a projector of a system of reflecting parts adapted to be oscillated about an axis or axes parallel with the optical of projection and about axes perpendicular to the plane of the film. The simplest form of my invention comprises ,a pair of reflecting mirrors oscillating about an axis parallel with the optical axis of projection and having their surfaces inclined 45 more or less to the optical axis. Such a. pair of mirrors are usually combined with two other similarly disposed mirrors for the purpose of maintaining relatively constant the optical axis from the light source to the film pictur My invention is more particularly descrlbed 1n the accompanying drawings, in Wl1lCl1- Figure 1 shows adiagrammatic plan view of the optical parts.

Figure 2 shows a side View of Figure 1.

Figure 3 shows a diagrammatic isometrical view illustrating the optical axis.

Figure 4 shows a. front view of the mechanism for operating the optical parts shown diagrammatically in Figures 1 and 2.

Figure shows a sectional side view on the line A,B of Figure 4.

Figure (3 shows a rear View of the operating mechanism.

Figur 7 shows a detail View of the yoke carrying the front pair of prisms.

Figure 8 shows a diagrammatic plan view of the optical parts in an alternative arrangement, and,

F igure 9 shows a side view of Figure 8.

Referring now to Figures 1 and 2 of the drawings the reflecting surfaces are arranged so that the first and last reflection, each of 90 is ellected by the mirrors 9 and f attached to arotatable spindle, the light being reflected through two more reflecting surfaces 6, c of 90 moving about another axis but parallel to the axis of the first and last reflecting surfaces 9 and f.

Figure 3 illustrates diagrammatically the optical axis which as shown is constant along A, B and E, F, but changing cyclically its position from C, D, to C, D, during the movement of the reflecting surfaces 9, f andc, 6 upon their axes.

Asuitable mechanism for operating the optical parts shown diagrammatically in Figures 1 and 2 is illustrated by Way of example in Figures 4, 5, 6 and 7. Therefleeting mirror 9 and the prism 7' are mounted upon the spindle 0 which is journalled upon the bracket l: which bracket is journalled upon a spindle mounted in the bearings m, m on the main framework p of the machine. The reflecting prism 7 connected by an arm on its rear ace as shown more particularly in l 'igue 5 through a link Z with a bell crank lever c ,pivotally mounted at a on the bracket q carried by the main framework 11). The free end of this bell crank lever is provided with a roller I) hearing upon the periphery of the main cam a mounted on the driving shaft a". It will .30 Qmounted on the same shaft as the main cam be readily,.understood thatthe rotation of the cam a -will-turn lever 'cand the link spindle o journalled {in bracket 7c.

Z, the prism f and con: sequently the reflecting hearings on the .In order that the secondary prisms, e, c

" may have a corresponding vmovement these I prisms are mounted on the yoke 6' shown in detail in Figure? which yoke is pivotally mounted particularly in Figure 4. The .yoke'c is 1 provided with an arm a on its rear face I, that by on their trunnions 'which arm is connected by the link (i with It will obvious this arrangement a simultaneous the hell crank lever c.

turning movement is given respectively to the pairs. of reflecting surfaces'g, f ande, e, v through the main cam 12/, and .bell'crank levers.

It is importantfto compensate for the curved nature of the path of light between f prisms e,' 0, resulting from the curvilinear motion applied curve in thesaid reflected light during this curvilinear motioml provide a downwardly depending arm on the pivotally mounted bracket .70 which carries said reflecting surfaces. This arm 10- lengageswith a cam a a. The cam out-is adapted to move said refiecting' surfaces g, f laterally through the bracket is carrying said surfaces during the half-turn movement given to said reflecting surfaces bythe main cam a. The film m is adapted to move through the gate 7* between the pair of reflecting surfaces 6, e as shown more particularly in Figures 5, 6 and 7. Oneside of the gate is mounted on the spindle 1' carried in thebracket r I lhe shutter sis mounted on the same spindle as the cams on anda This shutter is adapted to obscure the lens t during the return movement of the pairs of reflecting surfaces g, f, and e, e.

Motion is imparted to the mechanism operating the o tical parts through a handle or motor not s own, adapt/edto rotate the shaft a carrying the film feeding pulley a. This shaft is adapted to rotate through a counter-shaft and gearing; a wheel 1; driving the cam shaft operating theabove described mechanism.- The beam of light passes from a condenser through a fix'ed aperture plate 11) which considerably larger than picture Motion preferably by cam or "cams is imparted to all four reflecting' surfaces, whereby the optical axis through the whole S yStQHl'lS maintained constantly as in a straight line relatively to the centre of each picture. Means for framing the picture are preferably provided by a planetary or differential gear in circuit plate is preferably size.

through the bell crank surface g on their in the brackets as show-n more at. right angles to the angles to the r to the various reflectingsurfaces and in order to compensate forthe occurs wholly during a period means of a suitable items-e7 1 with the drive the film sprocket at the gate though a mere. jockey roller such as 7' may alternatively be used for this purpose.

' An: alternative form of my invention is illustrated diagrammatically in Figures 8 this form the light enters a' ically in Figures 8, and 9 is moved about a vertical axis under control of a suitable cam andv situated preferably behindthe projecting lens for compensating-this movement.

In constructing a small machine according to this invention and where a source of light such as a Nernst lamp might convenient-ly he used, I may omitthe first and second or light switchin mirrors but the area of nearly two pictures must be covered'bythe light and in this case a moving mask may be added behind the gate.

' Vhat ll claim is 1. Cinematograph' projector mechanism of the continuously moving filmkind, comprising a framework, means for continuously movlng a film mounted lnsaid framework, two systems ofrefiecting parts mounttroduced a glam plate shown diagrammat- I ed in said framework,- axes perpendicular to the film in the gate, means for oscillating said systems about said axes and a shutter mounted in said framework and adapted to he actuated by the operating mechanism synchronously with said oscillating system and said film moving means in such a manner that the reverse motion of said system of shutter ohturation. I

2. Cine'matograph projector mechanism of the continuously moving film kind, comprising a framework. means for continuously moving the film mounted in said,-

framework, a pair of reflectors pivotally mounted in said framework with reflecting surfaces inclined at an angle of 45fto the optical axis of projection, means for oscillating said reflectors about an axis parallel with said optical'axis, a second pair of reflectors pivotally mounted in said framework with reflecting surfaces "inclined at an angle of 45 to the optical axis of projection, means for oscillating said second pair of reflectors in the optical axis, and a shutter mounted in said framework and adapted to be actuated by the operating mechanism synchronously with said oscillating reflectors and said; film moving means in such a A manner that the reverse motion of said reflectors occurs wholly during a period of shutter obt-uration.

3. Cinematograph projector mechanism of the continuously moving film kind, comprising a framework, means for continuousthe optical axis from the light source to the film picture in a relatively constant position, means'for oscillating said second pair of fiectors synchronously with said first pair of reflectors and a shutter mounted in said framework and adapted to be actuated by the operating mechanism synchronously with said oscillating reflectors and said film moving means in such a manner that the reverse motion of said reflectors occurs wholly during a period of shutter obturation.

4:- Cinematograph projector mechanism of the continuously moving film kind, comprising a framework, :1 main driving shaft mounted in said framework, means for continuously moving the film mounted in said framework and driven by said main shaft, a counter-shaft adapted to be driven from said main driving shaft, cam mechanism mounted on said counter-shaft. a bell crank lever pivotally mounted in said framework and adapted to be rocked on its pivot by said came mechanism, a pair of reflectors pivotally mounted in said framework and inclined at an angle of -f5 to the optical axis of projection, a second pair of reflectors similarly disposed to the first pair of reflectors and mounted on the axes of the said first pair of reflectors and adapted to maintain the optical axis from the light source to the film picture in a relatively constant position, a film gate mounted in said framework between said pairs of reflectors, link mechanism connecting said bell crank lever with the axes of said reflectors and adapted to transmit to said reflectors through the camand bell crank lever an oscillation on their axes parallel with the optical axis and a shutter mounted in said framework and adapted to be actuated by the operating mechanism synchronously with said oscillating reflectors and said film moving means in such a manner that the re-- verse motion of said refiectol'soccurs wholly during a period of shutter obturation.

5. Cinematograph projector mechanism of the continuously moving film kind, comprising a framewor a main driving shaft mounted in said framework, means for continuously movin the film mounted in said framework and t riven by said main shaft, a

counter-shaft adapted to be driven from said main driving shaft, cam mechanism mounted on said counter-shaft, a bell crank lever pivotally mounted in said framework and adapted to be rocked on its pivot by said cam mechanism, a pair of reflectors pivotally mounted in said framework and inclined at an angle of 45 to the optical axis of projection, a second pair of reflectors similarly disposedto the first pair of reflectors and mounted on the axes of the said first. pair of reflectors and adapted to maintain the optical axis from the light source to the film picture in a relatively constant posi tion, a film gate mounted in said framework between said pairs of reflectors, link mechanism connecting said bell crank lever with the axes of said reflectors and adapted to transmit to said reflectors through the cam and bell crank lever an oscillation on their axes parallel with the optical axis and a shutter mounted on said cam shaft and adapted to obscurethe lens wholly during the reverse movement of said pairs of reflectors.

6. Cinematograph projector mechanism of the continuously moving film kind, comprising a framework, a main driving shaft mounted in said framework, a counter-shaft adapted to be driven from said main driving shaft, cam mechanism mounted on said counter-shaft, a second counter-shaft mountcd in said framework, a film feeding sprocket mounted on said second counter-shaft,means for driving saidcounter-shaft from said cam shaft independently of the other mechanism, a bell crank lever pivotallymounted in said framework and adapted to be rocked on its pivot by said cam mechanism, a pair of reflectors pivotally mounted in said framework and inclined at an angle of as to the optical axis of projection, a second pair of reflectors similarly disposed to the first pair of reflectors and mounted on the axes of the said first pair of'reflectors and adapted to maintain the optical axis from the light source to the fiim picture in a relatively constant position, a film gate mounted'in said framework between said pairs of re icctors. link mechanism connecting said bell crank lever-with the axes of said reflectors and adapted to transmit to said reflectors through the cam and bell crank lever an oscillation on their axes parallel with the optical axis and a shutter mounted-in said framework and adapted to tbe actuated by ing a framework, a main driving shaft mounted in said framework, means ,for continuously moving the film mounted insaid framework and drivenby said main shaft, a counter-shaft adaptedto be driven from said I main driving shaft, cam mechanism mounted on said counter-shaft, a bell crank-leverpivotally mounted in said framework and adapted to be rocked on its pivot bysaid cam mechanism, a pair of reflectors pivotally-mounted in said framework and inclined at an angle of 45 to the optical axis '0f projection,, 'a second pair? of. reflectors similarly dispiised to the first pair of reflectors and mounted on ,the-axes'of the said first pair .ofreflectors and adapted to maintain the optical axis from the light source to the film picture in a relatively constant position, a film gate mounted in said frame L work between said pairs of reflectors, link mechanism connecting said bell crank lever with the axes of said reflectors and adapted to transmit to said reflectors through the cam and bell crank lever an oscillation on their axesparallel with'the optical axis,means for compensating for the curved path of the beam of'light between the reflectors and a shutter mounted in said framework and adapted to be actuated by the operating mechanism synchronously with said oscillating reflectors and saidfilm moving means in such a manner that the reverse motion of said reflectors occurs wholly during a pe riod of shutter obtii'ration.

8. Cinematograph projector mechal'iisgn of the continuously moving film kind, comprising a framework, a main driving sliaft mounted in said framework, means for contin-uously moving the film mounted in said framework and driven by said main-shaft, a counter-shaft adapted to be driven from said main driving shaft, cam mechanism mounted on said counter-shaft, a bell crank lever pivotally mounted in said framework and til adapted to be rocked on its pivot by said cam mechanism, a bracket pivotally mounted in said framework, a. pair of reflectors carried by said bracket and inclined at an angle of 45 to the optical of projection, a second pair of reflectors similarly disposed to the first pair of reflectors and mounted on the axes of the said first pair of reflectors and adaptedto maintain the optical axis from the light source to the film picture ina' rela- -'tively constant position, a'film gate mounted in said framework between said pairs of reflectors, link mechanism connecting said bell crank lever with the axes of said reflectors and adapted to transmit to said reflectors through the cam andbell crank lever an oscillation on their .axesparallei -with the:

optical axis, an arm mounted on the bracket. carry-in said reflectors, a secondary cam mountedon saidcam shaft and adapted to engage said bracket arm to turn the bracket on its pivots and tomove said reflecting sur I faces laterally to compensate for the curved path of the beam of light betweenthe refleeting reflectors,.,anu a shutter mounted in' said frameworkaid adaptedto be actuated bythe operating mechanism synchronously with' said oscillating "reflectors and said film moving means in such a mannerthat the reverse motion of said reflectors occurs wholly during a period of shutterobturation.

v9. Cinematograph'"projector mechanism of the continuously moving fil-m 'kind, comprising a framework, a ma n driving shaft .mounted in s'aidframework, a counter-shaft adapted to be driven from said malndrivlng' shaft, cam mechanism mounted" on said counter-shaft, a second counter-shaft mount- 'ed in said framework, a film feeding sprocket mounted on said second counter-shaft, means for driving'said counter-shaft from said cam shaft independently of-the other mechanism, a bell crank lever p-ivotally mounted in said framework and adapted to be rocked on its pivotby said cam mechanism, a bracket pivotally mounted in said framework, a pair'of reflectors carriedby said bracket and inclined at an angle of 45 to the optical axis of projection, a second I pair of reflectors similarly disposed to the first pair of reflectors and mounted on the on t axes of they said first pair of reflectors and adapted to maintain the optical axis from I the light source to the film picture in a rela mounted onsaid-cam shaft and adapted to engage said bracket arm to turn the bracket on its pivots and to: move said reflecting surfaces laterally to compensate for the curved path of the beam oflight between the reflectors and a shutter mounted on said cam shaft and adapted to obscure the lens wholly during the reverse movement of said pairs of reflectors.

In testimony whereof I have signed my name to this specification.

e. B. BOWELL. 

